Posterior Column-Medial Lemniscus pathway (PCML) & Trigem. Nuclei

Question 1

What does the PCML pathway transmit?

Answer 1

Somatosensory - touch (texture, size, shape), tactile information and proprioception

Question 2

What is proprioception?

Answer 2

Knowing where your body is in space without seeing

Question 3

Primary afferent fibers

Answer 3

Sensory fibers

Question 4

Where do primary afferent fibers enter the spinal cord?

Answer 4

Medial division of posterior root

Question 5

What do the afferent fibers ascend as?

Answer 5

Posterior column

Question 6

Posterior column - grey or white matter?

Answer 6

White

Question 7

Afferent fibers from sacral level - T6 go where in the posterior column?

Answer 7

Fasciculus Gracilis

Question 8

Afferent fibers from T6 - superior go where in the posterior column?

Answer 8

Fasciculus cuneatus

Question 9

Where is the fasciculus gracilis?

Answer 9

Medial side of posterior column

Question 10

Where is the fasciculus cuneatus?

Answer 10

Lateral side of posterior column

Question 11

Afferent fibers from ex. T9 will go to what side of the posterior column?

Answer 11

Medial

Question 12

Afferent fibers from ex. T3 will go to what side of the posterior column?

Answer 12

Lateral

Question 13

What will lesions in the posterior column produce?

Answer 13

IPSILATERAL sensation loss at and below affected segment

Question 14

What is sensory ataxia?

Answer 14

Loss of reflexes and proprioception from extremities due to lack of sensory input

Question 15

How may a patient with sensory ataxia stand?

Answer 15

With a wide base to try and reestablish the proprioception

Question 16

If the fibers run in the fasciculus gracilis, where will they synapse?

Answer 16

Gracile nucleus

Question 17

If the fibers run in the fasciculus cuneatus, where will they synapse?

Answer 17

Cuneate nucleus

Question 18

2nd order neurons from either cuneate or gracile nucleus project where?

Answer 18

Contralateral thalamus

Question 19

Where are the cuneate and gracile nuclei located?

Answer 19

Posterior Medulla

Question 20

Once the fibers synapse at either the cuneate/gracile nuclei, then what happens?

Answer 20

They cross the midline and become the medial lemniscus

Question 21

Sensory decussation

Answer 21

Crossing midline

Question 22

How do fibers cross the midline at the posterior medulla?

Answer 22

Internal arcuate fibers

Question 23

Where do the 2nd order neurons synapse?

Answer 23

Contralateral thalamus - VPL

Question 24

Where do 3rd order neurons from the VPL project?

Answer 24

Primary Somatosensory cortex

Question 25

What is the blood supply to the VPL?

Answer 25

Posterior cerebral A.

Question 26

If the posterior cerebral A. is occluded, what will be affected?

Answer 26

Contralateral sensation of the body

Question 27

What is included in the primary somatosensory cortex (S1)?

Answer 27

Postcentral gyrus and posterior paracentral gyrus

Question 28

What body parts map to the posterior paracentral gyrus?

Answer 28

Foot, LE, hip

Question 29

What artery supplies the posterior paracentral gyrus?

Answer 29

Anterior cerebral A.

Question 30

If the anterior cerebral A. is occluded, what is affected?

Answer 30

Contralateral LE sensation

Question 31

What body parts map to the postcentral gyrus?

Answer 31

Chest, UE, face, throat

Question 32

What artery supplies the postcentral gyrus?

Answer 32

Middle cerebral A.

Question 33

If the middle cerebral A. is occluded, what is affected?

Answer 33

Contralateral chest, UE, face, throat sensation

Question 34

What inputs does the secondary somatosensory cortex receive?

Answer 34

Ipsilateral primary somatosensory cortex and VPI or thalamus

Question 35

If the parietal cortical regions have lesions, what occurs?

Answer 35

Agnosia - contralateral side

Question 36

What is agnosia?

Answer 36

Limb not recognized as part of patients own body but sensation is not super affected

Question 37

What are the 4 trigeminal nuclei?

Answer 37

Mesencephalic, principal sensory nucleus, spinal nucleus and trigeminal motor nucleus

Question 38

What afferent signals does the mesencephalic nucleus transmit?

Answer 38

Proprioception from TMJ, muscles of mastication and extraocular muscles

Question 39

What does the principal sensory nucleus transmit?

Answer 39

Touch and pressure

Question 40

Describe the orientation of the principal sensory nucleus

Answer 40

Face is oriented upside down - anteriorly = V1 and posteriorly = V3

Question 41

Anterior trigeminothalamic tracts project to which VPM of thalamus?

Answer 41

Contralateral

Question 42

Posterior trigeminothalamic tracts project to which VPM of thalamus?

Answer 42

Ipsilateral

Question 43

Which nucleus is the only one that has pseudopolar neurons?

Answer 43

Mesencephalic

Question 44

Describe the jaw jerk reflex

Answer 44

Stretch massater muscle down, axon synapses at trigeminal motor nuclues, and then both massaters contract -- testing trigeminal motor nucleus and V3